SMPS for tube HT

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ruffrecords

Well-known member
Joined
Nov 10, 2006
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Location
Norfolk - UK
I have had some success using switched mode power supplies (SMPS) for heater supplies so now I am thinking about using one for the  HT supply. It would need to supply about 340V at up to a couple of hundred milliamps. I have googled like mad but I have been unable to find anything close to what I need. Lots of LED constant current supplies but no high voltage constant voltage types (unless you want KV). I seem to remember Jakob found a small one  a while back but I cannot rememeber from where.

So, anyone know of any SMPS with 300V or more output?

Cheers

ian
 
zamproject said:

Something like that. This illustrates the confusion I get looking for this power supply. The one you linked to is listed as a DC-DC converter but in the detailed spec is syas the input voltage is 170 → 264V ac. Output current is a tad higher than I need!! but it is a start.

Cheers

Ian
 
Something along the lines of..

https://www.banggood.com/DC12-24V-to-DC200-450V-70W-High-Voltage-Converter-Step-Up-Power-Supply-Boost-Module-p-1051028.html

,

https://www.banggood.com/DC-DC-45-390V780V-ZVS-Boost-Module-High-Voltage-Capacitor-Charging-Adjustable-Regulator-Single-Outp-p-1160014.html

..or..

https://www.banggood.com/DC-DC-Boost-Converter-832V-to-45390V-High-Voltage-Charging-Booster-Module-40W-p-1100782.html

..maybe..?

Jakob E.
 
Thank you everyone for the replies so far:

Bangood: I think this was one mentioned by Jakob some time ago. I am a little concerned that some models have the idents filed off some of the ICs and there is no mention of safety and EMC approvals. Also, dc-dc conversion seems to me to be a bit of a round about way of getting the result. You need a lowish volts dc supply from which you then derive the high voltage one. What would be better would be ac mains in to HT dc out.

Cosel: seem to fit the bill but the output current is way over specified. Also looking at the manual you have to add your own input and output filtering plus inrush current protection etc.

XP: very low current and a dc-dc converter as well.

I appreciate the ideas but I think we are not quite there yet. I have asked Mean Well if they can make one. I'll let you know their response.

Cheers

Ian
 
The 10 amps of the Cossel is massive for any kind of tube amp , might be interesting to try for a power amplifier .Still 100 would buy you a nice chunk of Chinese iron too .
In the first stage of a smps you have the directly rectified mains voltage ,theres a few guys out there who tapped Ht from here ,then powered the fillaments off the same unit , not sure how safe that actually is .
The Dc- Dc boost system ,Up to down to get back up again ,its a bit of a merry go round.Ive seen cases of audible beat notes being created when different smps's interact
Comercially available units dont usually go above 40 or 50 volts .
Be interesting to see if the Mean well could come up with a one box solution though .

 
@Tubetec: you understand exactly where I am coming from. There is rectified mains in a regular SMPS. It is not much more than a 1:1 transformer to give a 340VDC output. As you say, regular SMPS only go up to 48V or so; anything above that seems to be a bit odd. Mean Well web site says they are expanding product range by 15% a year - maybe they could expand in the HT direction?

Cheers

Ian
 
ruffrecords said:
Bangood: I think this was one mentioned by Jakob some time ago. I am a little concerned that some models have the idents filed off some of the ICs and there is no mention of safety and EMC approvals.
...
I have asked Mean Well if they can make one. I'll let you know their response.

A couple of observations...

Wondering if the idents are obscured in the actual product or just for the photographs ?

They are modules as opposed to 'packaged' / end user units so can't be 'CE'marked although they could publish radiated and conducted emissions compared to relevant standards as some other manufacturers do (thinking XP here from memory).
Hopefully the mechanics of the module meet LVD requirements re creepage / clearance etc.

At 340V at , say, 230mA you are into having to meet PFC requirements - and I'm guessing there are other supplies in the finished product.

Will be interesting to see what response you get from Meanwell.
FWIW Whenever I've looked at custom design from a PSU manufacturer the cost vs quantity (low volume products) equation has seldom worked out except for critical high cost applications (eg X-ray supply).

 
Hi Ian,
Sounds like we might have a 'Thompson Bell' all tube console in the making there.
Would be kinda cool to be able to point to a one unit 19 inch rack mount when someone enquires about the power supply ,and not the usual boat anchor watt munching psu's of the olden days.
Including slow start for the ht unit might also be worth adding to the spec of the unit you want to build .
Keep up the good work .
 
many thanks for all the input.

I think a CE certified product is pretty much mandatory.

340V at 250mA is only 85W. Do all 85W SMPS include PFC? I know what PFC is but not the circumstances under which it becomes necessary to implement it.

The Thompson-Bell all tube console has been around for several years. There's one in a studio in Switzerland, another in Canada (two if you include Pierre's home built one using my PCBs) and then of course there is Holger's one metre wide 12 channel monster and there are at least three others currently under construction. It won't be long before we reach double figures.

I have looked at the Pete Millet design but it is, as you say, relatively low current and not CE approved.

I am familiar with ordering custom sub-assemblies like SMPS. Iput many products into volume production in China when I was at work. In those days, many CHinese manufacturers were not interested unless there was a million bucks of business in it for them. I am sure it is not much different today. Maybe I can persuade Mean Well it is a ripe marker for them?

I have one of the Bangood supplies. The chip idents really are filed off.

Cheers

Ian
 
I think they could do well from a line of compact, efficient ht psu's ,
I saw a guy demoing a dc dc step up convertor on youtube , he was able to draw amps out of it with almost no variation at all in ht volts ,it was impressive I have to say, one volt difference from zero to full load at 450volts  . I guess extra filtering of the smps outputs isnt all that big a deal, rf chokes are easy to find nowadays and it wont need huge caps either .
Cheers again,
 
ruffrecords said:
Do all 85W SMPS include PFC? I know what PFC is but not the circumstances under which it becomes necessary to implement it.
Probably not. IIRC, power factor isn't a strict requirement for consumer gear until you get to 500W.
 
ruffrecords said:
many thanks for all the input.

I think a CE certified product is pretty much mandatory.

340V at 250mA is only 85W. Do all 85W SMPS include PFC? I know what PFC is but not the circumstances under which it becomes necessary to implement it.

The Thompson-Bell all tube console has been around for several years. There's one in a studio in Switzerland, another in Canada (two if you include Pierre's home built one using my PCBs) and then of course there is Holger's one metre wide 12 channel monster and there are at least three others currently under construction. It won't be long before we reach double figures.

I have looked at the Pete Millet design but it is, as you say, relatively low current and not CE approved.

I am familiar with ordering custom sub-assemblies like SMPS. Iput many products into volume production in China when I was at work. In those days, many CHinese manufacturers were not interested unless there was a million bucks of business in it for them. I am sure it is not much different today. Maybe I can persuade Mean Well it is a ripe marker for them?

I have one of the Bangood supplies. The chip idents really are filed off.

Cheers

Ian

CE - well if it's a product that you are - in the jargon - "putting on the market" - then the final product needs to be CE marked (indicating conformance with ALL relevant product / safety etc standards) to be sold in the EU (and wherever else requires it - EFTA / EEA ?). Similarly there are similar requirements for other territories - FCC etc...
I guess you know this but just noting it here.

Last time I looked PFC is required at 75W+.
See the standard noted below.
BS EN 61000-3-2:2014
I don't have access to it atm.
Interesting guidance here:
http://www.epsma.org/PFCver100406_b.pdf
As always check for amendments / replacement etc...

Yeah - Far East customised design usually requires serious volume.

The ident filing doesn't inspire confidence !

Good Luck
 
While it is not elegant , one could try stacking 5 or 6 48v supplies.

I am curious if they would play nice together.
 
shabtek said:
While it is not elegant , one could try stacking 5 or 6 48v supplies.

I am curious if they would play nice together.

As it happens one of the day job products had that type of arrangement using VICOR modules on a common PCB.
Voltage is in the ballpark talked about here - 330V with a higher max current at 2A. It's a pulsed power / Capacitor Charging type application so have to bear that in mind.
It works but it comes out expensive and the thermal management was a 'challenge' at that power.

It has since been superceded by an in house design - two switch isolated flyback. In both cases the PFC is acheived on a separate mains input / boost converter module.
 
It would be great if there were a standard circuit for this. The right flyback transformer seems like the key component. Then make a PCB with whatever isolated flyback regulator chip. If it were adjustable one could use the same circuit for making a wide range of voltages and power.
 

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